Searches for lepton flavour violation in the tau -> 3mu decay with the ATLAS Experiment

味道不是一个基本的对称性，我们知道它在标准模型(SM)中被破坏了，无论是在中微子部门还是在夸克部门，通过混合。因此，人们自然会想到带电轻子气味破坏(CLFV)，但是，尽管G-2实验和B工厂有味道反常的迹象，但它在自然界中从未见过，它的观察将是超越SM物理的明确证据。虽然在电子和Muon通道中已经设置了严格的限制，但在tau情况下的限制要弱得多。Sburew物理学可能会与较重的tau产生更强的耦合，这使它成为研究的理想场所。该项目将使用完整的RUN-2和部分RUN-3 ATLAS数据，使用具有干净最终状态的黄金tau-&gt；3 MuonChannel来搜索LFV tau衰变。学生将首先分析在重口味腐烂中产生的tau，开发估计背景的方法和提取信号的多变量技术。在此之后，这项工作将扩展到W玻色子衰变中产生的牛子，并结合两次搜索的结果。总而言之，这些都有可能提供超出当前极限的灵敏度，如果没有观察到新的物理现象，就会设定对LFV tau衰变最严格的极限。该小组以前在W玻色子测量和在tau终态中的搜索方面都有广泛的经验。

Flavour is not a fundamental symmetry and we know that it is violated in theStandard Model (SM), both in the neutrino- and quark-sectors, via mixing. Itis thus natural to expect charged lepton flavour violation (cLFV) but, despitehints of flavour anomalies at g-2 experiment and B factories, it has neverbeen seen in nature and its observation would be unambiguous evidence ofbeyond the SM physics. While stringent limits have been set in the electronand muon channels, the constraints in the tau case are much weaker. Sincenew physics is likely to couple more strongly to the heavier tau, this makes itan ideal place to search. The project will search for LFV tau decays using thefull run-2 and partial run-3 ATLAS data using the golden tau -> 3 muonchannel, with its clean final state. The student will first analyse tau producedin heavy flavour decays, developing methods to estimate the backgroundsand multi-variate techniques to extract the signal. Following this, the workwill be extended to taus produced in W boson decays and the results of thetwo searches combined. Together, these have the potential to providesensitivity beyond the current limit and, if new physics is not observed, setthe most stringent limit on LFV tau decays. The group has previous wideexperience in both W boson measurements and searches in tau final states.